The copolymerization of styrene with N-phenyl maleimide in the presence of organomodified montmorillonite or Na+ montmorillonite was investigated. The conversion of the monomer was determined dilatometrically or gravimetrically. The copolymerization rate was accelerated and the polymerization activation energy in bulk and solution copolymerization decreased in the presence of montmorillonite. The tendency of alter-copolymerization was enhanced for bulk and solution polymerization, but not affected for emulsion polymerization, by the addition of organomodified montmorillonite or Na+ montmorillonite. X-ray diffraction studies showed that the methods of emulsion and bulk intercalative polymerization were more appropriate techniques for preparing nanocomposites with good dispersibility of clay. (c) 2005 Wiley Periodicals, Inc.